Tremendous efforts have been put into developing highly effective photocatalysts for pollution abatement. As for the most studied photocatalyst, titanium dioxide suffers from low sun light responsiveness (solar irradiation consisting of respectively, approximately 5% ultra-violet light, 43% visible light, and 52% harvestable infrared light); which defers its use for otherwise much wider industrial applications. The low sunlight responsiveness of TiO2 is mainly because of its large band gap which can only be activated by UV light. Accordingly, effort is required to modify TiO2 so as to enhance its catalytic efficiency.
TiO2 is commercially available in a form of nanoparticle which is considered to have large surface-to-volume ratio for enhancing catalytic performance. However, due to the small size of nanoparticle, it may be readily detached from a surface and inhaled by users who come across with the nanoparticle. The detachment of nanoparticles may raise health and environment concerns especially when the nanoparticles are positioned adjacent to an air stream or liquid stream. Therefore, even if a photocatalyst such as TiO2 is fabricated as nanoparticles, it may still have the above problems.